structure experiments – at higs
DESCRIPTION
Structure Experiments – at HIGS. @ 300 hrs are paid by DNDO. The Frontiers of Nuclear Science – A Long Range Plan (2007). “. [LRP, Nuclei: From Structure to Exploding Stars - What is the Origin of Simple Patterns in Nuclei, p 65]. ”. ⊗. 2 + FS. 2 + MS. 1 +. - PowerPoint PPT PresentationTRANSCRIPT
Experiment Spokesman Goal Running time
Thesis?
Scissors Mode Tonchev Analyze Scissors Mode excitations in actinide nuclei
500@
Pgymy Dipole Tonchev Analyze evolution of Pygmy Dipole resonance as a function of deformation
500
IVGQR Ahmed, Weller
Analyze IVGQR in A=30-200 nuclei evaluation resonance energy, width and EWSR – and compare with theory
500 2-3
Structure Experiments – at HIGS
@ 300 hrs are paid by DNDO
The Frontiers of Nuclear Science – A Long Range Plan (2007)
[LRP, Nuclei: From Structure to Exploding Stars- What is the Origin of Simple Patterns in Nuclei, p 65]
“
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2-phonon excitations:
⊗1-
Found at sum energy of one-phononstates: ~ 3 MeV
Found usuallybetween 2.7-3.6 MeV
Proton-Neutron symmetric Existence because of nuclear 2-fluid system
⊗2+FS 2+
MS
1+
Dipole Excitation Below 4 MeV: Scissors Mode Tonchev
Scissors mode systematics: clearly collective Degree of fragmentation depends on deformation
Dipole Excitation Below 4 MeV
Proposed Experiments
Where we are going: study the scissor mode in actinide nuclei
1. Completed experiments: 235U, 238U, 232Th.
2. To be measured: 239Pu, 237Np, 233U.
3. Working with the theorist to develop a model (RPA-based) to reproduce all experimental observables of the E1 and M1
excitations for actinides nuclei.
Interpretation of the Pygmy Resonance in QPM calculations Tonchev
PDR is predominantly E1 mode of excitation
PDR is enhanced strength below the GDR
We unveiled the fine structure of the M1 spin-flip mode
Evidence for surface neutron density oscillations
“Soft dipole mode“ at ~7 MeV is mixture of isoscalar and isovector components
N. Tsoneva, H. Lenske, PRC 77, 024321 (2008), A.P. Tonchev et al. NIM B 241, 51474 (2005); A.P. Tonchev et al. AIP 819, 350 (2006); AIP 1090, 74 (2009); A.P. Tonchev et al. PRL 104 072501 (2010).
p n
What we have learned ?
Fine and Gross Structure of the PDR in 138Ba
A. Tonchev et al., PRL 104, 072501 (2010)
Fine structure Gross structure
Pygmy Dipole Resonance Impact
Nuclear astrophysics: r-process 1998 S. Goriely PLB2003 M. Arnold et al. PR2005 T. Rauscher NPA
Neutrino-less double-beta decay physics2004 J. Bahcall et al. PRD
Extract the γ-ray transition matrix elements for the decay (QRPA)
Study of the structure difference of the initial and final states
Study of the nuclear dipole response in 76Se and 76Ge isotopes
Testing the nuclear models for stable and extrapolating to exotic nuclei1998 S. Goriely, PLB; 2008 G. Rusev ,PRC
Neutron radius: PDR provides experimental constrains on properties of nuclear matter (neutron skin and symmetry energy)
2006 Piekarewicz PRC
124Xe
Present Experimental Activity with N=82 Nuclei
130XeZ=54
N=8
2
138Ba
140Ce
142Nd
144Sm
Completed measurements at HIGS
p,n n
N/Z
1.32
1.37
1.41
1.46
154Sm154Sm
2
0.09
0.10
0.09
0.09
Proposed measurements
136Xe132Xe
• Predicted dependence on N/Z ratio weak isospin effect
134Xe
B(E1) [10-3e2fm2]
536
576
600
960
Proposed Experiment
1. PDR as a function of deformation 144 148 152 154 Sm62
N/Z 1.32 1.39 1.45 1.48 ↑
2 0.09 0.14 0.31 0.34 ↑
Increased deformation with N/Z
128 130 132 134 136 Xe54
N/Z 1.37 1.41 1.44 1.48 1.52 ↑
2 0.18 0.17 0.14 0.12 0.09 ↓
Decreased deformation with N/Z
F. Dönau et. al. PRC 76, 014317 (2007); G. Rusev et al. PRC 73, 044308 (2006); G. Rusev et al., PRC (2009)
QRPA calculations
N
PDR region
An example – 209Bi
IVGQR
odd± (E)
Weller, Ahmed
209Bi Results
209Bi Results – Notice Quality of Our data
209Bi Results – Notice Quality of Our data